statement has no effect inspection

python/src/com/jetbrains/python/PyBundle.properties

@@ -184,6 +184,9 @@ INSP.NAME.raising.new.style.class=Raising a new style class
 # PyDocstringInspection
 INSP.NAME.docstring=Missing or empty docstring
 
+# PyStatementEffectInspection
+INSP.NAME.statement.effect=Statement has no effect 
+
 # Refactoring
 # introduce
 refactoring.introduce.name.error=Incorrect name

python/src/com/jetbrains/python/inspections/PyStatementEffectInspection.java

@@ -0,0 +1,70 @@
+package com.jetbrains.python.inspections;
+
+import com.intellij.codeInspection.LocalInspectionTool;
+import com.intellij.codeInspection.ProblemsHolder;
+import com.intellij.psi.PsiElementVisitor;
+import com.intellij.psi.util.PsiTreeUtil;
+import com.jetbrains.python.PyBundle;
+import com.jetbrains.python.psi.*;
+import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Created by IntelliJ IDEA.
+ * Author: Alexey.Ivanov
+ * Date:   10.03.2010
+ * Time:   17:35:16
+ */
+public class PyStatementEffectInspection extends LocalInspectionTool {
+  @Nls
+  @NotNull
+  @Override
+  public String getGroupDisplayName() {
+    return PyBundle.message("INSP.GROUP.python");
+  }
+
+  @Nls
+  @NotNull
+  @Override
+  public String getDisplayName() {
+    return PyBundle.message("INSP.NAME.statement.effect");
+  }
+
+  @NotNull
+  @Override
+  public String getShortName() {
+    return "PyStatementEffectInspection";
+  }
+
+  @NotNull
+  @Override
+  public PsiElementVisitor buildVisitor(@NotNull ProblemsHolder holder, boolean isOnTheFly) {
+    return new Visitor(holder);
+  }
+
+  private static class Visitor extends PyInspectionVisitor {
+
+    public Visitor(final ProblemsHolder holder) {
+      super(holder);
+    }
+
+    @Override
+    public void visitPyExpressionStatement(PyExpressionStatement node) {
+      PyExpression expression = node.getExpression();
+      if (expression instanceof PyCallExpression || expression instanceof PyYieldExpression) {
+        return;
+      }
+      PyTryPart tryPart = PsiTreeUtil.getParentOfType(node, PyTryPart.class);
+      if (tryPart != null) {
+        final PyStatementList statementList = tryPart.getStatementList();
+        if (statementList == null) {
+          return;
+        }
+        if (statementList.getStatements().length == 1 && statementList.getStatements()[0] == node) {
+          return;
+        }
+      }
+      registerProblem(expression, "Statement seems to have no effect");
+    }
+  }
+}

python/src/com/jetbrains/python/inspections/PythonInspectionToolProvider.java

@@ -29,8 +29,9 @@ public class PythonInspectionToolProvider implements InspectionToolProvider {
       PyExceptionInheritInspection.class,
       PyDefaultArgumentInspection.class,
       PyRaisingNewStyleClassInspection.class,
+      PyDocstringInspection.class,
       PyUnboundLocalVariableInspection.class,
-      PyDocstringInspection.class
+      PyStatementEffectInspection.class
     };
   }
 }

python/testData/inspections/PyStatementEffectInspection/expected.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems>
+  <problem>
+    <file>test.py</file>
+    <line>1</line>
+    <description>Statement seems to have no effect</description>
+  </problem>
+  <problem>
+    <file>test.py</file>
+    <line>2</line>
+    <description>Statement seems to have no effect</description>
+  </problem>
+  <problem>
+    <file>test.py</file>
+    <line>5</line>
+    <description>Statement seems to have no effect</description>
+  </problem>
+</problems>

python/testSrc/com/jetbrains/python/PythonInspectionsTest.java

@@ -142,4 +142,9 @@ public class PythonInspectionsTest extends PyLightFixtureTestCase {
     LocalInspectionTool inspection = new PyDocstringInspection();
     doTest(getTestName(false), inspection);
   }
+
+  public void testPyStatementEffectInspection() throws Throwable {
+    LocalInspectionTool inspection = new PyStatementEffectInspection();
+    doTest(getTestName(false), inspection);
+  }
 }